PTO grinds when I press the clutch in

[SPYDERLK]

The implement free wheels to a stop when I press the clutch. The throttle has nothingno do with it.

Yes, but when your bushog is spinning without load - tractor stationary, clutch out - and you throttle down the engine abruptly, does the bh slow right along with the engine or does it coast down more slowly? An overunning clutch should let the bh continue to spin fast as the engine rpm dies down. Due to its own friction, the bh will finally slow to the point that the slowed engine is again driving it - it just wont follow the engine down like its geared to it because the o/r clutch only transfers power one way. I would expect there to be the same clicking anytime the bh was spinning faster than the engine drive.
larry